Safety tool joint



H. E. GRAU 2,204,586

SAFETY TOOL JOINT Filed. June 15, 4958 Patented June 18, 1940- UNITED STATES PATENT OFFICE SAFETY TOOL JOINT V Herbert 1:. Gran, Vernon, Calif., minor a Byron-Jackson 00., Huntington Park, CaliL, corporation of Delaware Application June 15, 1938, Serial No. 213,792

3 Claims. (Cl. 285-146) This invention relates to safety tool joints such as employed in drilling wells by the rotary method. With this method of drilling, it sometimes happens that the drill bit or other rotary tool will become stuck or frozen in the hole, and when it is attempted to free the tool by rotating the drill string in the reverse direction, some one of the standard joints in the drill string will unscrew and disconnect the upper part of the drill string from the lower part. This would make it necessary to commence a fishing job to remove the lower portion of the drill string from the hole.

The level at which the disconnection occurs may be anywhere between the well bottom and the ground level. And hence such a disconnection may greatly delay the progress of the drilling, and may occasion considerable expense in conducting the operation of removing the drill sections remaining in the hole.

Hence safety tool joints of this type are usually placed in a string of drill rod or tubing just above the bit or drill collar, so that if the bit should become stuck in the hole, the drill stringcan be rotated in the reverse direction, causing the safety joint to unscrew without unscrewing any of the regulation tool joints. Thus the string of pipe can be removed from the hole quicklyv and fishing tools can be run in the hole to recover the stuck bit. I

30 It is an object of the present invention to provide a safety joint which will readily release when necessary, but which will have the strength of a regulation tool joint and having substantially the same outside and inside dimensions so as not to 35 interfere with the use of other tools which grip U118 pipe on the outside or are run inside the D De.

Another object is to provide a releasing safety joint of simple and relatively inexpensive construction, which will be reliable in operation, that is to say, which can be depended upon to unscrew and release with less torque than the standard joints used throughout the length of the drill string.

45 In practice, it is necessary to maintain the condition of the working parts of the joint intact to prevent corrosion, and insure-that the joint will release with a predetermined torque. Hence another object is to provide means for protecting the working parts of the joint to accomplish this, but without increasing the outside diameter of the joint.

Another object is to provide simple and dc pendable means for insuring that the joint will 65 release at a predetermined torque. v

Other objects and advantages of the invention will be apparent from the following description of a preferred embodiment of the invention.

The invention consists. in the novel parts and 60 combination of parts to be described hereinafter,v

all of which contribute to produce an eflicient safety tool joint.

Invention also resides in the method employed in constructing and screwing up the drill string.

In the drawing: 5 n Fig. 1 is a side elevation and partial section of a drill string embodying my invention and indicating the preferred location of my safety tool joint in the drill string.

Fig. 2 is a partial side elevation and partial section through a safety joint embodying my invention, and showing the same disconnected from the drill string.

Fig. 3 is a fragmentary section upon an enlarged scale and further illustrating details of the packing means for packing off the interior of my safety joint. This view illustrates the packing construction at the upper end of the joint.

Fig. 4 is a view similar to Fig. 3, but illustrating the packing construction at the lower end of the joint.

Fig. 5 is a vertical section upon an enlarged scale, illustrating a modified embodiment for packing at the upper end of the joint,

Before proceeding to a more detailed description of the invention, it should be stated that in practicing the invention, I provide the drill string with a special joint that comprises two members with a thread connection between the same. I construct this joint so that its resistance to unscrewing will be less than that of the regular threaded joints in the tool string. In order to accomplish this I prefer to make the pitch of the thread connecting these two members higher than the thread connections for the rod, or tubing, sections of thedrill string. Furthermore, I prefer to provide abutting shoulders on the two members, that form. the joint, which abut against each other when the joint is tightened up. The regular or standard joints that connect the sections of the drill string, are also provided with shoulders that abutwhen the joints are tightened up. In accordance with my invention, I apply the same torque in tightening my safety joint as is employed in tightening up the regular joints of the tool string. By reason of this fact and the fact that the pitch of the thread in my special joint is higher than the thread of the regular joints of the tool string, when his necessary to rotate the drill string in a reverse direction to get it loose, from a stuck bit, my special joint will unscrew with less torque than that of the other joints of the tool string. Hence the disconnection will be'accomplished just above the bit. The tool string can then be pulled from the well in the regular way, and fishing tools employed to recover the bit. 7

In practice, it is preferableto form the abutting shoulders between the regular joints of the drill string, of slightly larger area than the abutting shoulders of the two members that compose my special joint, and it is also preferable to employ hardened steel washers between the shoulders in my special joint. These features cooperate to insure that it will require less torque to "break my special joint than it will to break any of the other joints in the tool string.

In order to insure that the necessary torque to unscrew my special joint will not vary by any substantial amount, it is preferable to provide for packing oil" the interior of the joint; that is to say, the portion of the joint that comprises the threads. This prevents any possibility of corrosion of these threads in such a way as to increase their resistance in the unscrewing movement.

In Fig. 1 I illustrate a drill string I provided with my releasing joint 2 connected into the string just above a drill collar 3 that is illustrated as carrying an ordinary fish-tail bit I. This drill string i may be composed of drill rods or drill tubing. In the present instance, the drill string is illustrated as composed of sections 5 of tubing. In any case, the sections of the drill string would be connected by threaded joints.

When using tubing, the sections 5 would be connected together by couplings 6 having tapered threaded connections I. It is preferable to employ a drill collar or sub 8 connected to the upper end of my releasing joint 2.

Referring to Figure comprises two telescoping members comprising an inner sleeve 9 of reduced diameter, having an enlarged head In at its lower end, said head carrying a tapered threaded pin I I having the stand-v ard thread employed in the drill string, and of considerably smaller diameter than the head i0. so that a shoulder I2 is formed around the root of the pin ll. At the upper end of the head iii an annular shoulder i3 is formed similar to the shoulder l2, but of slightly less diameter, so that the area of .the shoulder I2 is greater than that of the shoulder l3 for a-purpose that will appear hereinafter.

My releasable joint also includes an outer sleeve M, which telescopes overthe upper end of the inner sleeve, and between these two sleeves there is a thread connection. l5. This thread connection and the shoulders l2 and I3 cooperate in such a way that when it is necessary to disconnect the drill by reverse rotation, the releasable connection 2 will disconnect before any of the joints in. the drill string. This effect is enhanced by reason of the increased area for the shoulder l2, which will increase the resistance to rotation at this point, to unscrew the threaded pin 1 I from its box or socket It in the upper end of the drill collar 3. In addition to this, and in order to insure that the sleeves of this joint 2 will unscrew by the application of less torque than will any of the joints in the drill string, I prefer to make the pitch of the thread connection l5 considerably greater than the pitch of the regular threaded joints or thread connections I throughout the length of the drill string.

. In screwing up the drill string, I tighten up the joint 2 with substantially the same torque that I employ in tightening up all of the other joints of the drill string. By reason of the novel features of construction of the joint referred to above, and by reason of the fact that the same torque is used for tightening up the releasable joint, this joint will unscrew with less torque than the other screw connections of the string.

It will be noted that the lower end of the 2, the releasing coupling outer sleeve l4 presents an end face or shoulder" H, which could abut directly against the annular shoulder 13 of the head l0 when the two members constituting the releasable joint are two hardened metal anti-friction washers l8,-

which are preferably of non-corroding material such as hardened stainless steel. The contacting faces between these two hardened steel rings is are, of course, finished and polished so that very slight actual frictional resistance would be offered to turning one of these washers on the other and, of course, the contact point between these two washers would be the point where the joint would break.

The upper end of the outer sleeve I4 is formed with a tapered threaded box l9 to enable it to connect to a drill collar or sub 8 carried by the lower end of the tool string. However, it should be understood that in using the joint, either end of the joint can be disposed uppermost. In other words, a pin such as the pin ll, could be employed at the upper end of the joint instead of at the lower end. There is, however, a practical advantage in having the box is disposed uppermost because in that case the hardened steel rings l8 are supported on the shoulder 13 and hence they cannot drop into the weli when the parts of the joint 2 are disconnected.

The washers 18 are preferably of non-corroding material such as stainless steel, and should be hardened and ground. These rings may be beveled at their edges if desired. The use of this bevel enables the surface area of contact of these two rings to be cut down to any area desired to insure that this area will be smaller than the area of contact at the shoulder l2; and to insure that while these rings can operate to resist thrust and. enable torque to be applied through the joint and its threads in operating the drill, these areas of contact will not offer great resistance to the torque necessary to unscrew the joint.

In a drilling safety joint it is essential that packing means be provided for preventing leakage of drilling fluid into or out of the joint because such leakage would quickly corrode or cut out the threads. This is accomplished in the present instance by means of sealing rings placed at the upper and lower ends of the thread connection [5. The lower sealing ring 20 comprises a channel-shaped ring of oil-proof rubber or other flexible material. The ring 20 is positioned with the channel facing downwardly and is confined within an annular channel formed by the walls of a recess 2i in the member 9 and a recess 22 in the member I. with this organization of parts it will be evident that external fluid pressure leaking past the rings is will cause the lips of the sealing ring 20 to press against the walls of its retaining recesses and effectively seal the joint between the lower ends of members 9 and I. The wall of the recess 22 is preferably tapered outwardly and downwardly as indicated so that as the members 9 and I4 are set up or screwed up tight, the outer lip of the flexible sealing ring 22 is pressed against the wall I 22 to insure that the lip of the channel will be upper end of sleeve 9. Several holes '21 are provided extending through the sleeve 9 to admit fluid to the sealing ring 23 to cause the ring to seal against inner-wall of member 4.

In order to provide against possible leakage past ring 22, it is preferable to provide the second sealing ring 24. This ring has an upwardly facing channel 28 and extends across the joint between the members 9 and I4 below the ring 23. The ring 24 is positioned in a circumferential groove 29 formed in the outer surfaces of the member 9. a

In order to make the sealing ring 24 more effective, the bore of the member is formed inside diameter as shown at 3| members 9 and I4.

The inner face of member I4 is tapered downwardly and outwardly so as to present a substantially conical face as indicated at 32 to insure that the outer lip of the sealing ring 24 will be slightly compressed insure that it will at the bore 30.

In operation, the members 9 and are attached to a string of pipe, as illustrated in Fig. 1. The members9 and I 4 are screwed together in the usual manner and with the same force as is used in making up the regulation joints such as at the coupling 6. Owing tothe large lead angle or pitch of the threads IS, the pressure on the thrust washers It will be very much less than on the shoulders of the other and regulation joints. This fact, together with the, fact that the rings l9 are stainless, hardened and ground smooth, permits the members 9 and I4 to release with much less torque than the regulation joints. I t

Thednner and outer sealing rings described above, effectively prevent leakage through the Joint in either direction so that the joint can be used while drilling. i Figure 5 illustrates a slightly modified form of the invention in which ing ring at the inner end of the inner sleeve 9.

different position than either the rings 22 or 24. A chamelshaped sealing ring 33 having its channel facing radially inwardly, is confined between the upper end 'of the sleeve 9 and a downwardly facing shoulder 24 formed in the member l4. The sealing ring 32 is effective, under relatively light pressures, for sealing the threads l5 against leakage from the bore 35 to the threads IS, in an outward direction.

The washers l8 are preferably formed with ground flat upper and lower faces.

By reason of the fact that the grooves 29 and press against the sealed joint 29 are formed in the faceof the inner member of the joint, it will be evident that the presence of these grooves does not necessitate any increase in the outside diameter of the joint. This is one of the advantages of this joint.

The words drill string" in the claims include when in position, to

thread connection either a string of drill pipe, or tubing, or pump rods.

It is understood that the embodiment of the invention described herein is only one of the manyembodiments this invention may take, and I do not wish to be limited in the practice or the invention, nor in the claims,'to the particular embodiment set forth.

What I claim is:

1. In a safety releasing drill string, the combination of a series 'of drill string sections with threaded joints connecting the same, a special joint capable of being more readily disconnected than said first named joints connected into the drill string near its lower end, said joint com-- prising two members with a thread connection between the same of higher pitch than the thread connections of said drill string sections, said two members having abutting shoulders, and a hardened anti-friction thrust washer clamped between said shoulders, said shoulders and said washer cooperating to enable the said joint to unscrew with less torque than the other threaded connections.

2. In a safety releasing drill string, the combination of a series of drill string sections with threaded joints connecting the same, a special joint capable of being more readily disconnected than said first named joints connected into the drill string near its lower end, said joint comprising two members with a thread connection between the same of higher pitch than the thread connections of said drill string sections, said twomembers having abutting shoulders with a plurality of anti-friction hardened thrust washers of corrosion-resistant material, clamped between the said shoulders, said shoulders and said washers cooperating to enable the said joint to unscrew with less "torque than the other threaded connections.

, '3. In a safety releasing drill string, the'combination of a series of drill string sections with threaded joints connecting the same, a special 4 joint capable of being more readily disconnected than said first named joints comprising an upper member with a threaded box atits upper end for connecting; the same at thelowe'rend of the drill string, said member extending upwardly into the upper member from below, and having means at its lower end for effecting its connection to the drill tool, a thread connection connecting said members of higher pitch than the thread connections of said drill string sections, said lower member having a substantially cylindrical neck above the thread connection between said memspecial joint including a lower' bers,'the upper member having a-substantially cylindrical bore to receive said neck, said neck having circumferential grooves formed therein, packing within said grooves for excluding liquids flowing down the drill stringfrom penetrating to the thread connection between said members,

said lower member having a circumferentialgroove in the same below the lower end of the between said members, packing "received within the same, said lower member further having an'annular shoulder below the last-named packing, and a hardened antifriction washer clamped between the last-named shoulder and the lower end of said upper member.

. T E. GRAU. 

